Lionboy

Charlie Ashanti is the son of two scientists who are kidnapped as the result of a dramatic discovery they've made (the cure for asthma, which is rampant in this near-future world). Ten-year-old Charlie decides to go in search of them, and uses his ability to speak Cat (which he's had ever since he was scratched by a leopard as a baby) to gain helpful information. The local cats of London point him in the right direction and even deliver messages from him to his parents and back. When Charlie finds himself aboard a floating circus that's heading to Paris, he befriends the circus lions, who become his further accomplices. He'll help them escape the circus as this first book in a trilogy draws to a close.